PDP-11/53+ Jumpers

From: Jonathan Engdahl <engdahl_at_cle.ab.com>
Date: Wed Jun 6 08:46:55 2001

----- Original Message -----
From: <healyzh_at_aracnet.com>
To: <classiccmp>
> > Does anyone have the jumpers for a PDP-11/53+ CPU board?
> > --
> > Eric Dittman
> > dittman_at_dittman.net
> This is a FAQ, and sadly no one seems to, either on the list
or elsewhere.
> If anyone has them I need them also.
> Zane

I know of four people that are looking for this information.

There used to be a pdf of "EK-OLCP5-TM-001 Micro/PDP-11 System
Technical Manual" on www.retrobytes.org, but that site is gone
and the new owner of the domain name has no knowledge of the
doc. I have not been able to find another copy on the web.

Antonio Carlini has a copy of that pdf. He uploaded it to
www.vararchive.org a couple days ago. I have not yet been able
to find it at the archive. Evidently the maintainer hasn't got
around to it yet. I know what that's like. I'll wait a few days
before I bug him. Or perhaps, if the vaxarchive is going to be a
problem, someone could provide a more appropriate place that
Antonio can upload the doc to.

Are vax.sevensages.org and www.vaxarchive.org the same place,
different, or is one a mirror of the other? The vaxarchive
address seems to be down at the moment.

I have discovered the most needed information by following
traces and by trial and error. I have the console connections
and the baud rate jumpers documented at

The board we are talking about is the M7554. The older layout is
the one pictured in the Visual Field Guide. There is a picture
of the newer one on my web page. The new one is a completely new
layout, and can have up to 1.5 megs of RAM.

I have found you can obtain one of these boards for around $50
on eBay -- either $50 for a board, or $10 for a DECserver 500 or
550 plus $40 shipping for all the iron around it. The DECserver
550 has the M7554-SD, with an 18 MHz, rev -09 CPU, and 1.5 megs
onboard. The 500 has the M7554-PB, which is the older layout,
with only .5 megs RAM. The CPU is -07. The field guide says
the -PB is 18 MHz -- I have not yet verified this is true for my

I haven't got around to burning the 11/53 ROMs yet, but that
doesn't matter if you use a 3rd party disk controller with a
boot ROM onboard. Change the address of the disk controller's
boot ROM, and use ODT to boot from there. All three boards that
I've tried so far have booted and run RT-11 just fine using this
method. I used the -PB board to boot UNIX, and it seems to run

I ohmed out the DECserver front panel, and I'll get that info
posted eventuallly. But you really don't need the front panel or
ROMs to run RT-11 or UNIX, just the console connection. Cut off
the end of a PC floppy cable -- it fits the console connector.
It will even boot RT-11 with the ROMS removed.

Jonathan Engdahl             Rockwell Automation
Principal Research Engineer  24800 Tungsten Road
Advanced Technology          Euclid, OH 44117  USA
Euclid Labs                  http://users.safeaccess.com/engdahl
Received on Wed Jun 06 2001 - 08:46:55 BST

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